Navigated surgical system with eye to xr headset display calibration

ABSTRACT

A camera tracking system for computer assisted navigation during surgery operatively determines a first pose of a second extended-reality (XR) headset relative to stereo tracking cameras located on a first XR headset based on first tracking information from the stereo tracking cameras. The camera tracking system determines a second pose of eyes of a user wearing the second XR headset relative to the stereo tracking cameras located on the first XR headset based on second tracking information from the stereo tracking cameras. The camera tracking system also calibrates an eye-to-display relationship defining pose of the eyes of the user wearing the second XR headset to a display device of the second XR headset based on the determined first and second poses. The camera tracking system also controls where symbols are displayed on the display device of the second XR headset based on the eye-to-display relationship.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 16/902,715, filed Jun. 16, 2020, which is incorporated hereinby reference.

FIELD

The present disclosure relates to medical devices and systems, and moreparticularly, camera tracking systems used for computer assistednavigation during surgery.

BACKGROUND

Computer assisted navigation in surgery provides surgeons with enhancedvisualization of surgical instruments with respect to radiographicimages of the patient's anatomy. Navigated surgeries typically includecomponents for tracking the position and orientation of surgicalinstruments via arrays of disks or spheres using a single stereo camerasystem.

Eye tracking can have major advantages in wearable extended realitydisplay systems. Eye tracking allows for more accurate overlays ofvirtual content displayed on the physical world, and proper warping ofthe frames being sent to the displays for more realistic content.

Eye tracking, unfortunately, can be expensive, bulky, and difficult tointegrate. It normally requires 2-4 cameras as well as infrared strobeswhich need to see/shine on the pupils to be mounted inside of a headset.This set up requires specific positioning of the eye tracker which maynot be possible in certain headset/optic designs. One additionaldownfall to adding the necessary equipment is that the additions alsoincrease the weight and size of an augmented reality headset.

SUMMARY

Various embodiments disclosed herein are directed to improvements in eyetracking for calibrating pose of a user's eyes to a display device of anextended reality (XR) headset during computer assisted navigation duringsurgery.

In one embodiment, a camera tracking system for computer assistednavigation during surgery operatively determines a first pose of asecond XR headset relative to stereo tracking cameras located on a firstXR headset based on first tracking information from the stereo trackingcameras. The camera tracking system determines a second pose of eyes ofa user wearing the second XR headset relative to the stereo trackingcameras located on the first XR headset based on second trackinginformation from the stereo tracking cameras. The camera tracking systemalso calibrates an eye-to-display relationship defining pose of the eyesof the user wearing the second XR headset to a display device of thesecond XR headset based on the determined first and second poses. Thecamera tracking system also controls where symbols are displayed on thedisplay device of the second XR headset based on the eye-to-displayrelationship.

Related methods by a camera tracking system and related computer programproducts are disclosed.

Other camera tracking systems, methods, and computer program productsaccording to embodiments will be or become apparent to one with skill inthe art upon review of the following drawings and detailed description.It is intended that all such camera tracking systems, methods, andcomputer program products be included within this description, be withinthe scope of the present disclosure, and be protected by theaccompanying claims. Moreover, it is intended that all embodimentsdisclosed herein can be implemented separately or combined in any wayand/or combination.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the disclosure and are incorporated in a constitute apart of this application, illustrate certain non-limiting embodiments ofinventive concepts. In the drawings:

FIG. 1 illustrates an embodiment of a surgical system according to someembodiments of the present disclosure;

FIG. 2 illustrates a surgical robot component of the surgical system ofFIG. 1 according to some embodiments of the present disclosure;

FIG. 3A illustrates a camera tracking system component of the surgicalsystem of FIG. 1 according to some embodiments of the presentdisclosure;

FIGS. 3B and 3C illustrate a front view and isometric view of anothercamera tracking system component which may be used with the surgicalsystem of FIG. 1 according to some embodiments of the presentdisclosure;

FIG. 4 illustrates an embodiment of an end effector that is connectableto a robot arm and configured according to some embodiments of thepresent disclosure;

FIG. 5 illustrates a medical operation in which a surgical robot and acamera system are disposed around a patient;

FIG. 6 illustrates a block diagram view of the components of thesurgical system of FIG. 5 being used for a medical operation;

FIG. 7 illustrates various display screens that may be displayed on thedisplay of FIGS. 5 and 6 when using a navigation function of thesurgical system;

FIG. 8 illustrates a block diagram of some electrical components of asurgical robot according to some embodiments of the present disclosure;

FIG. 9 illustrates a block diagram of components of a surgical systemthat includes imaging devices connected to a computer platform which canbe operationally connected to a camera tracking system and/or surgicalrobot according to some embodiments of the present disclosure;

FIG. 10 illustrates an embodiment of a C-Arm imaging device that can beused in combination with the surgical robot in accordance with someembodiments of the present disclosure;

FIG. 11 illustrates an embodiment of an O-Arm imaging device that can beused in combination with the surgical robot in accordance with someembodiments of the present disclosure;

FIG. 12 illustrates a block diagram view of the components of a surgicalsystem that includes a pair of XR headsets and an auxiliary tracking barwhich operate in accordance with some embodiments of the presentdisclosure;

FIG. 13 illustrates an XR headset which is configured in accordance withsome embodiments of the present disclosure;

FIG. 14 illustrates electrical components of the XR headset that can beoperatively connected to a computer platform, imaging device(s), and/ora surgical robot in accordance with some embodiments of the presentdisclosure;

FIG. 15 illustrates a block diagram showing arrangement of opticalcomponents of the XR headset in accordance with some embodiments of thepresent disclosure;

FIG. 16 illustrates an example view through the display screen of an XRheadset for providing navigation assistance to manipulate a surgicaltool during a medical procedure in accordance with some embodiments ofthe present disclosure;

FIG. 17 illustrates an example configuration of an auxiliary trackingbar having two pairs of stereo cameras configured in accordance withsome embodiments of the present disclosure;

FIG. 18 illustrates a block diagram view of the components of a surgicalsystem that includes tracking cameras in a pair of XR headsets and in anauxiliary tracking bar which collectively operate in accordance withsome embodiments of the present disclosure;

FIG. 19 illustrates an embodiment of two users wearing XR headsetsoperative to track each other's eyes in accordance with some embodimentsof the present disclosure;

FIG. 20 illustrates an embodiment of one user wearing an XR headsetoperative to tracking the user's eyes using a reflective surfaceaccordance with some embodiments of the present disclosure;

FIG. 21 illustrates an embodiment of tracking coordinate systems for twoXR headsets in accordance with some embodiments of the presentdisclosure; and

FIGS. 22, 23, and 24 illustrate flow charts of operations performed by acamera tracking system for calibrating eye-to-XR headset displays andresponsively controlling where symbols are displayed on XR headsets inaccordance with some embodiments.

DETAILED DESCRIPTION

Inventive concepts will now be described more fully hereinafter withreference to the accompanying drawings, in which examples of embodimentsof inventive concepts are shown. Inventive concepts may, however, beembodied in many different forms and should not be construed as limitedto the embodiments set forth herein. Rather, these embodiments areprovided so that this disclosure will be thorough and complete, and willfully convey the scope of various present inventive concepts to thoseskilled in the art. It should also be noted that these embodiments arenot mutually exclusive. Components from one embodiment may be tacitlyassumed to be present or used in another embodiment.

Various embodiments disclosed herein are directed to improvements incomputer assisted navigation during surgery. An extended reality (XR)headset is operatively connected to the surgical system and configuredto provide an interactive environment through which a surgeon,assistant, and/or other personnel can view and select among patientimages, view and select among computer generated surgery navigationinformation, and/or control surgical equipment in the operating room. Aswill be explained below, the XR headset may be configured to augment areal-world scene with computer generated XR images. The XR headset maybe configured to provide an augmented reality (AR) viewing environmentby displaying the computer generated XR images on a see-through displayscreen that allows light from the real-world scene to pass therethroughfor combined viewing by the user. Alternatively, the XR headset may beconfigured to provide a virtual reality (VR) viewing environment bypreventing or substantially preventing light from the real-world scenefrom being directly viewed by the user while the user is viewing thecomputer generated AR images on a display screen. An XR headset can beconfigured to provide both AR and VR viewing environments. In oneembodiment, both AR and VR viewing environments are provided by lateralbands of substantially differing opacity arranged between thesee-through display screen and the real-world scene, so that a VRviewing environment is provided for XR images aligned with a highopacity band and an AR viewing environment is provided for XR imagesaligned with the low opacity band. In another embodiment, both AR and VRviewing environments are provided by computer adjustable control of anopacity filter that variably constrains how much light from thereal-world scene passes through a see-through display screen forcombining with the XR images viewed by the user. Thus, the XR headsetcan also be referred to as an AR headset or a VR headset.

FIG. 1 illustrates an embodiment of a surgical system 2 according tosome embodiments of the present disclosure. Prior to performance of anorthopedic or other surgical procedure, a three-dimensional (“3D”) imagescan may be taken of a planned surgical area of a patient using, e.g.,the C-Arm imaging device 104 of FIG. 10 or O-Arm imaging device 106 ofFIG. 11, or from another medical imaging device such as a computedtomography (CT) image or MRI. This scan can be taken pre-operatively(e.g. few weeks before procedure, most common) or intra-operatively.However, any known 3D or 2D image scan may be used in accordance withvarious embodiments of the surgical system 2. The image scan is sent toa computer platform in communication with the surgical system 2, such asthe computer platform 910 of the surgical system 900 (FIG. 9) which mayinclude the camera tracking system component 6, the surgical robot 4(e.g., robot 2 in FIG. 1), imaging devices (e.g., C-Arm 104, O-Arm 106,etc.), and an image database 950 for storing image scans of patients. Asurgeon reviewing the image scan(s) on a display device of the computerplatform 910 (FIG. 9) generates a surgical plan defining a target posefor a surgical tool to be used during a surgical procedure on ananatomical structure of the patient. Example surgical tools, alsoreferred to as tools, can include, without limitation, drills, screwdrivers, retractors, and implants such as a screws, spacers, interbodyfusion devices, plates, rods, etc. In some embodiments, the surgicalplan defining the target plane is planned on the 3D image scan displayedon a display device.

As used herein, the term “pose” refers to the position and/or therotational angle of one object (e.g., dynamic reference array, endeffector, surgical tool, anatomical structure, etc.) relative to anotherobject and/or to a defined coordinate system. A pose may therefore bedefined based on only the multidimensional position of one objectrelative to another object and/or to a defined coordinate system, onlyon the multidimensional rotational angles of the object relative toanother object and/or to a defined coordinate system, or on acombination of the multidimensional position and the multidimensionalrotational angles. The term “pose” therefore is used to refer toposition, rotational angle, or combination thereof.

The surgical system 2 of FIG. 1 can assist surgeons during medicalprocedures by, for example, holding tools, aligning tools, using tools,guiding tools, and/or positioning tools for use. In some embodiments,surgical system 2 includes a surgical robot 4 and a camera trackingsystem component 6. The ability to mechanically couple surgical robot 4and camera tracking system component 6 can allow for surgical system 2to maneuver and move as a single unit, and allow surgical system 2 tohave a small footprint in an area, allow easier movement through narrowpassages and around turns, and allow storage within a smaller area.

A surgical procedure may begin with the surgical system 2 moving frommedical storage to a medical procedure room. The surgical system 2 maybe maneuvered through doorways, halls, and elevators to reach a medicalprocedure room. Within the room, the surgical system 2 may be physicallyseparated into two separate and distinct systems, the surgical robot 4and the camera tracking system component 6. Surgical robot 4 may bepositioned adjacent the patient at any suitable location to properlyassist medical personnel. Camera tracking system component 6 may bepositioned at the base of the patient, at the patient shoulders, or anyother location suitable to track the present pose and movement of thepose of tracks portions of the surgical robot 4 and the patient.Surgical robot 4 and camera tracking system component 6 may be poweredby an onboard power source and/or plugged into an external wall outlet.

Surgical robot 4 may be used to assist a surgeon by holding and/or usingtools during a medical procedure. To properly utilize and hold tools,surgical robot 4 may rely on a plurality of motors, computers, and/oractuators to function properly. Illustrated in FIG. 1, robot body 8 mayact as the structure in which the plurality of motors, computers, and/oractuators may be secured within surgical robot 4. Robot body 8 may alsoprovide support for robot telescoping support arm 16. The size of robotbody 8 may provide a solid platform supporting attached components, andmay house, conceal, and protect the plurality of motors, computers,and/or actuators that may operate attached components.

Robot base 10 may act as a lower support for surgical robot 4. In someembodiments, robot base 10 may support robot body 8 and may attach robotbody 8 to a plurality of powered wheels 12. This attachment to wheelsmay allow robot body 8 to move in space efficiently. Robot base 10 mayrun the length and width of robot body 8. Robot base 10 may be about twoinches to about 10 inches tall. Robot base 10 may cover, protect, andsupport powered wheels 12.

In some embodiments, as illustrated in FIG. 1, at least one poweredwheel 12 may be attached to robot base 10. Powered wheels 12 may attachto robot base 10 at any location. Each individual powered wheel 12 mayrotate about a vertical axis in any direction. A motor may be disposedabove, within, or adjacent to powered wheel 12. This motor may allow forsurgical system 2 to maneuver into any location and stabilize and/orlevel surgical system 2. A rod, located within or adjacent to poweredwheel 12, may be pressed into a surface by the motor. The rod, notpictured, may be made of any suitable metal to lift surgical system 2.The rod may lift powered wheel 10, which may lift surgical system 2, toany height required to level or otherwise fix the orientation of thesurgical system 2 in relation to a patient. The weight of surgicalsystem 2, supported through small contact areas by the rod on eachwheel, prevents surgical system 2 from moving during a medicalprocedure. This rigid positioning may prevent objects and/or people frommoving surgical system 2 by accident.

Moving surgical system 2 may be facilitated using robot railing 14.Robot railing 14 provides a person with the ability to move surgicalsystem 2 without grasping robot body 8. As illustrated in FIG. 1, robotrailing 14 may run the length of robot body 8, shorter than robot body8, and/or may run longer the length of robot body 8. Robot railing 14may further provide protection to robot body 8, preventing objects andor personnel from touching, hitting, or bumping into robot body 8.

Robot body 8 may provide support for a Selective Compliance ArticulatedRobot Arm, hereafter referred to as a “SCARA.” A SCARA 24 may bebeneficial to use within the surgical system 2 due to the repeatabilityand compactness of the robotic arm. The compactness of a SCARA mayprovide additional space within a medical procedure, which may allowmedical professionals to perform medical procedures free of excessclutter and confining areas. SCARA 24 may comprise robot telescopingsupport 16, robot support arm 18, and/or robot arm 20. Robot telescopingsupport 16 may be disposed along robot body 8. As illustrated in FIG. 1,robot telescoping support 16 may provide support for the SCARA 24 anddisplay 34. In some embodiments, robot telescoping support 16 may extendand contract in a vertical direction. The body of robot telescopingsupport 16 may be any width and/or height configured to support thestress and weight placed upon it.

In some embodiments, medical personnel may move SCARA 24 through acommand submitted by the medical personnel. The command may originatefrom input received on display 34, a tablet, and/or an XR headset (e.g.,headset 920 in FIG. 9) as will be explained in further detail below. TheXR headset may eliminate the need for medical personnel to refer to anyother display such as the display 34 or a tablet, which enables theSCARA 24 to be configured without the display 34 and/or the tablet. Thecommand may be generated by the depression of a switch and/or thedepression of a plurality of switches, and/or may be generated based ona hand gesture command and/or voice command that is sensed by the XRheadset as will be explained in further detail below.

As shown in FIG. 5, an activation assembly 60 may include a switchand/or a plurality of switches. The activation assembly 60 may beoperable to transmit a move command to the SCARA 24 allowing an operatorto manually manipulate the SCARA 24. When the switch, or plurality ofswitches, is depressed the medical personnel may have the ability tomove SCARA 24 through applied hand movements. Alternatively oradditionally, an operator may control movement of the SCARA 24 throughhand gesture commands and/or voice commands that are sensed by the XRheadset as will be explained in further detail below. Additionally, whenthe SCARA 24 is not receiving a command to move, the SCARA 24 may lockin place to prevent accidental movement by personnel and/or otherobjects. By locking in place, the SCARA 24 provides a solid platformthrough which the end effector 26 can guide a surgical tool during amedical procedure.

Robot support arm 18 can be connected to robot telescoping support 16 byvarious mechanisms. In some embodiments, best seen in FIGS. 1 and 2,robot support arm 18 rotates in any direction in regard to robottelescoping support 16. Robot support arm 18 may rotate three hundredand sixty degrees around robot telescoping support 16. Robot arm 20 mayconnect to robot support arm 18 at any suitable location and by variousmechanisms that enable rotation in any direction relative to robotsupport arm 18. In one embodiment, the robot arm 20 can rotate threehundred and sixty degrees relative to the robot support arm 18. Thisfree rotation allows an operator to position robot arm 20 according to asurgical plan.

The end effector 26 shown in FIGS. 4 and 5 may attach to robot arm 20 inany suitable location. The end effector 26 can be configured to attachto an end effector coupler 22 of the robot arm 20 positioned by thesurgical robot 4. The example end effector 26 includes a tubular guidethat guides movement of an inserted surgical tool relative to ananatomical structure on which a surgical procedure is to be performed.

In some embodiments, a dynamic reference array 52 is attached to the endeffector 26. Dynamic reference arrays, also referred to as “DRAB”herein, are rigid bodies which may be disposed on an anatomicalstructure (e.g., bone) of a patient, one or more XR headsets being wornby personnel in the operating room, the end effector, the surgicalrobot, a surgical tool in a navigated surgical procedure. The computerplatform 910 in combination with the camera tracking system component 6or other 3D localization system are configured to track in real-time thepose (e.g., positions and rotational orientations) of the DRA. The DRAcan include fiducials, such as the illustrated arrangement of balls.This tracking of 3D coordinates of the DRA can allow the surgical system2 to determine the pose of the DRA in any multidimensional space inrelation to the target anatomical structure of the patient 50 in FIG. 5.

As illustrated in FIG. 1, a light indicator 28 may be positioned on topof the SCARA 24. Light indicator 28 may illuminate as any type of lightto indicate “conditions” in which surgical system 2 is currentlyoperating. In some embodiments, the light may be produced by LED bulbs,which may form a ring around light indicator 28. Light indicator 28 maycomprise a fully permeable material that can let light shine through theentirety of light indicator 28. Light indicator 28 may be attached tolower display support 30. Lower display support 30, as illustrated inFIG. 2 may allow an operator to maneuver display 34 to any suitablelocation. Lower display support 30 may attach to light indicator 28 byany suitable mechanism. In some embodiments, lower display support 30may rotate about light indicator 28 or be rigidly attached thereto.Upper display support 32 may attach to lower display support 30 by anysuitable mechanism.

In some embodiments, a tablet may be used in conjunction with display 34and/or without display 34. The tablet may be disposed on upper displaysupport 32, in place of display 34, and may be removable from upperdisplay support 32 during a medical operation. In addition the tabletmay communicate with display 34. The tablet may be able to connect tosurgical robot 4 by any suitable wireless and/or wired connection. Insome embodiments, the tablet may be able to program and/or controlsurgical system 2 during a medical operation. When controlling surgicalsystem 2 with the tablet, all input and output commands may beduplicated on display 34. The use of a tablet may allow an operator tomanipulate surgical robot 4 without having to move around patient 50and/or to surgical robot 4.

As will be explained below, in some embodiments a surgeon and/or otherpersonnel can wear XR headsets that may be used in conjunction withdisplay 34 and/or a tablet or the XR head(s) may eliminate the need foruse of the display 34 and/or tablet.

As illustrated in FIGS. 3A and 5, camera tracking system component 6works in conjunction with surgical robot 4 through wired or wirelesscommunication networks. Referring to FIGS. 1, 3 and 5, camera trackingsystem component 6 can include some similar components to the surgicalrobot 4. For example, camera body 36 may provide the functionality foundin robot body 8. Robot body 8 may provide an auxiliary tracking bar uponwhich cameras 46 are mounted. The structure within robot body 8 may alsoprovide support for the electronics, communication devices, and powersupplies used to operate camera tracking system component 6. Camera body36 may be made of the same material as robot body 8. Camera trackingsystem component 6 may communicate directly to an XR headset, tabletand/or display 34 by a wireless and/or wired network to enable the XRheadset, tablet and/or display 34 to control the functions of cameratracking system component 6.

Camera body 36 is supported by camera base 38. Camera base 38 mayfunction as robot base 10. In the embodiment of FIG. 1, camera base 38may be wider than robot base 10. The width of camera base 38 may allowfor camera tracking system component 6 to connect with surgical robot 4.As illustrated in FIG. 1, the width of camera base 38 may be largeenough to fit outside robot base 10. When camera tracking systemcomponent 6 and surgical robot 4 are connected, the additional width ofcamera base 38 may allow surgical system 2 additional maneuverabilityand support for surgical system 2.

As with robot base 10, a plurality of powered wheels 12 may attach tocamera base 38. Powered wheel 12 may allow camera tracking systemcomponent 6 to stabilize and level or set fixed orientation in regardsto patient 50, similar to the operation of robot base 10 and poweredwheels 12. This stabilization may prevent camera tracking systemcomponent 6 from moving during a medical procedure and may keep cameras46 on the auxiliary tracking bar from losing track of a DRA connected toan XR headset and/or the surgical robot 4, and/or losing track of one ormore DRAs 52 connected to an anatomical structure 54 and/or tool 58within a designated area 56 as shown in FIGS. 3A and 5. This stabilityand maintenance of tracking enhances the ability of surgical robot 4 tooperate effectively with camera tracking system component 6.Additionally, the wide camera base 38 may provide additional support tocamera tracking system component 6. Specifically, a wide camera base 38may prevent camera tracking system component 6 from tipping over whencameras 46 is disposed over a patient, as illustrated in FIGS. 3A and 5.

Camera telescoping support 40 may support cameras 46 on the auxiliarytracking bar. In some embodiments, telescoping support 40 moves cameras46 higher or lower in the vertical direction. Camera handle 48 may beattached to camera telescoping support 40 at any suitable location andconfigured to allow an operator to move camera tracking system component6 into a planned position before a medical operation. In someembodiments, camera handle 48 is used to lower and raise cameratelescoping support 40. Camera handle 48 may perform the raising andlowering of camera telescoping support 40 through the depression of abutton, switch, lever, and/or any combination thereof.

Lower camera support arm 42 may attach to camera telescoping support 40at any suitable location, in embodiments, as illustrated in FIG. 1,lower camera support arm 42 may rotate three hundred and sixty degreesaround telescoping support 40. This free rotation may allow an operatorto position cameras 46 in any suitable location. Lower camera supportarm 42 may connect to telescoping support 40 by any suitable mechanism.Lower camera support arm 42 may be used to provide support for cameras46. Cameras 46 may be attached to lower camera support arm 42 by anysuitable mechanism. Cameras 46 may pivot in any direction at theattachment area between cameras 46 and lower camera support arm 42. Inembodiments a curved rail 44 may be disposed on lower camera support arm42.

Curved rail 44 may be disposed at any suitable location on lower camerasupport arm 42. As illustrated in FIG. 3A, curved rail 44 may attach tolower camera support arm 42 by any suitable mechanism. Curved rail 44may be of any suitable shape, a suitable shape may be a crescent,circular, oval, elliptical, and/or any combination thereof. Cameras 46may be movably disposed along curved rail 44. Cameras 46 may attach tocurved rail 44 by, for example, rollers, brackets, braces, motors,and/or any combination thereof. Motors and rollers, not illustrated, maybe used to move cameras 46 along curved rail 44. As illustrated in FIG.3A, during a medical procedure, if an object prevents cameras 46 fromviewing one or more DRAs being tracked, the motors may responsively movecameras 46 along curved rail 44. This motorized movement may allowcameras 46 to move to a new position that is no longer obstructed by theobject without moving camera tracking system component 6. While cameras46 is obstructed from viewing one or more tracked DRAs, camera trackingsystem component 6 may send a stop signal to a surgical robot 4, XRheadset, display 34, and/or a tablet. The stop signal may prevent SCARA24 from moving until cameras 46 has reacquired tracked DRAs 52 and/orcan warn an operator wearing the XR headset and/or viewing the display34 and/or the tablet. This SCARA 24 can be configured to respond toreceipt of a stop signal by stopping further movement of the base and/orend effector coupler 22 until the camera tracking system can resumetracking of DRAs.

FIGS. 3B and 3C illustrate a front view and isometric view of anothercamera tracking system component 6′ which may be used with the surgicalsystem of FIG. 1 or may be used independent of a surgical robot. Forexample, the camera tracking system component 6′ may be used forproviding navigated surgery without use of robotic guidance. One of thedifferences between the camera tracking system component 6′ of FIGS. 3Band 3C and the camera tracking system component 6 of FIG. 3A, is thatthe camera tracking system component 6′ of FIGS. 3B and 3C includes ahousing that transports the computer platform 910. The computer platform910 can be configured to perform camera tracking operations to trackDRAs, perform navigated surgery operations that provide surgicalnavigation information to a display device, e.g., XR headset and/orother display device, and perform other computational operationsdisclosed herein. The computer platform 910 can therefore include anavigation computer, such as one or more of the navigation computers ofFIG. 14.

FIG. 6 illustrates a block diagram view of the components of thesurgical system of FIG. 5 used for the medical operation. Referring toFIG. 6, the tracking cameras 46 on the auxiliary tracking bar has anavigation field-of-view 600 in which the pose (e.g., position andorientation) of the reference array 602 attached to the patient, thereference array 604 attached to the surgical instrument, and the robotarm 20 are tracked. The tracking cameras 46 may be part of the cameratracking system component 6′ of FIGS. 3B and 3C, which includes thecomputer platform 910 configured to perform the operations describedbelow. The reference arrays enable tracking by reflecting light in knownpatterns, which are decoded to determine their respective poses by thetracking subsystem of the surgical robot 4. If the line-of-sight betweenthe patient reference array 602 and the tracking cameras 46 in theauxiliary tracking bar is blocked (for example, by a medical personnel,instrument, etc.), further navigation of the surgical instrument may notbe able to be performed and a responsive notification may temporarilyhalt further movement of the robot arm 20 and surgical robot 4, displaya warning on the display 34, and/or provide an audible warning tomedical personnel. The display 34 is accessible to the surgeon 610 andassistant 612 but viewing requires a head to be turned away from thepatient and for eye focus to be changed to a different distance andlocation. The navigation software may be controlled by a tech personnel614 based on vocal instructions from the surgeon.

FIG. 7 illustrates various display screens that may be displayed on thedisplay 34 of FIGS. 5 and 6 by the surgical robot 4 when using anavigation function of the surgical system 2. The display screens caninclude, without limitation, patient radiographs with overlaid graphicalrepresentations of models of instruments that are positioned in thedisplay screens relative to the anatomical structure based on adeveloped surgical plan and/or based on poses of tracked referencearrays, various user selectable menus for controlling different stagesof the surgical procedure and dimension parameters of a virtuallyprojected implant (e.g. length, width, and/or diameter).

For navigated surgery, various processing components (e.g., computerplatform 910) and associated software described below are provided thatenable pre-operatively planning of a surgical procedure, e.g., implantplacement, and electronic transfer of the plan to computer platform 910to provide navigation information to one or more users during theplanned surgical procedure.

For robotic navigation, various processing components (e.g., computerplatform 910) and associated software described below are provided thatenable pre-operatively planning of a surgical procedure, e.g., implantplacement, and electronic transfer of the plan to the surgical robot 4.The surgical robot 4 uses the plan to guide the robot arm 20 andconnected end effector 26 to provide a target pose for a surgical toolrelative to a patient anatomical structure for a step of the plannedsurgical procedure.

Various embodiments below are directed to using one or more XR headsetsthat can be worn by the surgeon 610, the assistant 612, and/or othermedical personnel to provide an improved user interface for receivinginformation from and/or providing control commands to the surgicalrobot, the camera tracking system component 6/6′, and/or other medicalequipment in the operating room.

FIG. 8 illustrates a block diagram of some electrical components of thesurgical robot 4 according to some embodiments of the presentdisclosure. Referring to FIG. 8, a load cell (not shown) may beconfigured to track force applied to end effector coupler 22. In someembodiments the load cell may communicate with a plurality of motors850, 851, 852, 853, and/or 854. As load cell senses force, informationas to the amount of force applied may be distributed from a switch arrayand/or a plurality of switch arrays to a controller 846. Controller 846may take the force information from load cell and process it with aswitch algorithm. The switch algorithm is used by the controller 846 tocontrol a motor driver 842. The motor driver 842 controls operation ofone or more of the motors 850, 851, 852, 853, and 854. Motor driver 842may direct a specific motor to produce, for example, an equal amount offorce measured by load cell through the motor. In some embodiments, theforce produced may come from a plurality of motors, e.g., 850-854, asdirected by controller 846. Additionally, motor driver 842 may receiveinput from controller 846. Controller 846 may receive information fromload cell as to the direction of force sensed by load cell. Controller846 may process this information using a motion controller algorithm.The algorithm may be used to provide information to specific motordrivers 842. To replicate the direction of force, controller 846 mayactivate and/or deactivate certain motor drivers 842. Controller 846 maycontrol one or more motors, e.g. one or more of 850-854, to inducemotion of end effector 26 in the direction of force sensed by load cell.This force-controlled motion may allow an operator to move SCARA 24 andend effector 26 effortlessly and/or with very little resistance.Movement of end effector 26 can be performed to position end effector 26in any suitable pose (i.e., location and angular orientation relative todefined three-dimensional (3D) orthogonal reference axes) for use bymedical personnel.

Activation assembly 60, best illustrated in FIG. 5, may form of abracelet that wraps around end effector coupler 22. The activationassembly 60 may be located on any part of SCARA 24, any part of endeffector coupler 22, may be worn by medical personnel (and communicatewirelessly), and/or any combination thereof. Activation assembly 60 maycomprise of a primary button and a secondary button.

Depressing primary button may allow an operator to move SCARA 24 and endeffector coupler 22. According to one embodiment, once set in place,SCARA 24 and end effector coupler 22 may not move until an operatorprograms surgical robot 4 to move SCARA 24 and end effector coupler 22,or is moved using primary button. In some examples, it may require thedepression of at least two non-adjacent primary activation switchesbefore SCARA 24 and end effector coupler 22 will respond to operatorcommands. Depression of at least two primary activation switches mayprevent the accidental movement of SCARA 24 and end effector coupler 22during a medical procedure.

Activated by primary button, load cell may measure the force magnitudeand/or direction exerted upon end effector coupler 22 by an operator,i.e. medical personnel. This information may be transferred to one ormore motors, e.g. one or more of 850-854, within SCARA 24 that may beused to move SCARA 24 and end effector coupler 22. Information as to themagnitude and direction of force measured by load cell may cause the oneor more motors, e.g. one or more of 850-854, to move SCARA 24 and endeffector coupler 22 in the same direction as sensed by the load cell.This force-controlled movement may allow the operator to move SCARA 24and end effector coupler 22 easily and without large amounts of exertiondue to the motors moving SCARA 24 and end effector coupler 22 at thesame time the operator is moving SCARA 24 and end effector coupler 22.

In some examples, a secondary button may be used by an operator as a“selection” device. During a medical operation, surgical robot 4 maynotify medical personnel to certain conditions by the XR headset(s) 920,display 34 and/or light indicator 28. The XR headset(s) 920 are eachconfigured to display images on a see-through display screen to form anextended reality image that is overlaid on real-world objects viewablethrough the see-through display screen. Medical personnel may beprompted by surgical robot 4 to select a function, mode, and/or assessthe condition of surgical system 2. Depressing secondary button a singletime may activate certain functions, modes, and/or acknowledgeinformation communicated to medical personnel through the XR headset(s)920, display 34 and/or light indicator 28. Additionally, depressing thesecondary button multiple times in rapid succession may activateadditional functions, modes, and/or select information communicated tomedical personnel through the XR headset(s) 920, display 34 and/or lightindicator 28.

With further reference to FIG. 8, electrical components of the surgicalrobot 4 include platform subsystem 802, computer subsystem 820, motioncontrol subsystem 840, and tracking subsystem 830. Platform subsystem802 includes battery 806, power distribution module 804, connector panel808, and charging station 810. Computer subsystem 820 includes computer822, display 824, and speaker 826. Motion control subsystem 840 includesdriver circuit 842, motors 850, 851, 852, 853, 854, stabilizers 855,856, 857, 858, end effector connector 844, and controller 846. Trackingsubsystem 830 includes position sensor 832 and camera converter 834.Surgical robot 4 may also include a removable foot pedal 880 andremovable tablet computer 890.

Input power is supplied to surgical robot 4 via a power source which maybe provided to power distribution module 804. Power distribution module804 receives input power and is configured to generate different powersupply voltages that are provided to other modules, components, andsubsystems of surgical robot 4. Power distribution module 804 may beconfigured to provide different voltage supplies to connector panel 808,which may be provided to other components such as computer 822, display824, speaker 826, driver 842 to, for example, power motors 850-854 andend effector coupler 844, and provided to camera converter 834 and othercomponents for surgical robot 4. Power distribution module 804 may alsobe connected to battery 806, which serves as temporary power source inthe event that power distribution module 804 does not receive power froman input power. At other times, power distribution module 804 may serveto charge battery 806.

Connector panel 808 may serve to connect different devices andcomponents to surgical robot 4 and/or associated components and modules.Connector panel 808 may contain one or more ports that receive lines orconnections from different components. For example, connector panel 808may have a ground terminal port that may ground surgical robot 4 toother equipment, a port to connect foot pedal 880, a port to connect totracking subsystem 830, which may include position sensor 832, cameraconverter 834, and DRA tracking cameras 870. Connector panel 808 mayalso include other ports to allow USB, Ethernet, HDMI communications toother components, such as computer 822. In accordance with someembodiments, the connector panel 808 can include a wired and/or wirelessinterface for operatively connecting one or more XR headsets 920 to thetracking subsystem 830 and/or the computer subsystem 820.

Control panel 816 may provide various buttons or indicators that controloperation of surgical robot 4 and/or provide information from surgicalrobot 4 for observation by an operator. For example, control panel 816may include buttons to power on or off surgical robot 4, lift or lowervertical column 16, and lift or lower stabilizers 855-858 that may bedesigned to engage casters 12 to lock surgical robot 4 from physicallymoving. Other buttons may stop surgical robot 4 in the event of anemergency, which may remove all motor power and apply mechanical brakesto stop all motion from occurring. Control panel 816 may also haveindicators notifying the operator of certain system conditions such as aline power indicator or status of charge for battery 806. In accordancewith some embodiments, one or more XR headsets 920 may communicate, e.g.via the connector panel 808, to control operation of the surgical robot4 and/or to received and display information generated by surgical robot4 for observation by persons wearing the XR headsets 920.

Computer 822 of computer subsystem 820 includes an operating system andsoftware to operate assigned functions of surgical robot 4. Computer 822may receive and process information from other components (for example,tracking subsystem 830, platform subsystem 802, and/or motion controlsubsystem 840) in order to display information to the operator. Further,computer subsystem 820 may provide output through the speaker 826 forthe operator. The speaker may be part of the surgical robot, part of anXR headset 920, or within another component of the surgical system 2.The display 824 may correspond to the display 34 shown in FIGS. 1 and 2.

Tracking subsystem 830 may include position sensor 832 and cameraconverter 834. Tracking subsystem 830 may correspond to the cameratracking system component 6 of FIG. 3. The DRA tracking cameras 870operate with the position sensor 832 to determine the pose of DRAs 52.This tracking may be conducted in a manner consistent with the presentdisclosure including the use of infrared or visible light technologythat tracks the location of active or passive elements of DRAs 52, suchas LEDs or reflective markers, respectively.

Functional operations of the tracking subsystem 830 and the computersubsystem 820 can be included in the computer platform 910, which can betransported by the camera tracking system component 6′ of FIGS. 3A and3B. The tracking subsystem 830 can be configured to determine the poses,e.g., location and angular orientation of the tracked DRAs. The computerplatform 910 can also include a navigation controller that is configuredto use the determined poses to provide navigation information to usersthat guides their movement of tracked tools relative toposition-registered patient images and/or tracked anatomical structuresduring a planned surgical procedure. The computer platform 910 candisplay information on the display of FIGS. 3B and 3C and/or to one ormore XR headsets 920. The computer platform 910, when used with asurgical robot, can be configured to communicate with the computersubsystem 820 and other subsystems of FIG. 8 to control movement of theend effector 26. For example, as will be explained below the computerplatform 910 can generate a graphical representation of a patient'sanatomical structure, surgical tool, user's hand, etc. with a displayedsize, shape, color, and/or pose that is controlled based on thedetermined pose(s) of one or more the tracked DRAs, and which thegraphical representation that is displayed can be dynamically modifiedto track changes in the determined poses over time.

Motion control subsystem 840 may be configured to physically movevertical column 16, upper arm 18, lower arm 20, or rotate end effectorcoupler 22. The physical movement may be conducted through the use ofone or more motors 850-854. For example, motor 850 may be configured tovertically lift or lower vertical column 16. Motor 851 may be configuredto laterally move upper arm 18 around a point of engagement withvertical column 16 as shown in FIG. 2. Motor 852 may be configured tolaterally move lower arm 20 around a point of engagement with upper arm18 as shown in FIG. 2. Motors 853 and 854 may be configured to move endeffector coupler 22 to provide translational movement and rotation alongin about three-dimensional axes. The computer platform 910 shown in FIG.9 can provide control input to the controller 846 that guides movementof the end effector coupler 22 to position a passive end effector, whichis connected thereto, with a planned pose (i.e., location and angularorientation relative to defined 3D orthogonal reference axes) relativeto an anatomical structure that is to be operated on during a plannedsurgical procedure. Motion control subsystem 840 may be configured tomeasure position of the end effector coupler 22 and/or the end effector26 using integrated position sensors (e.g. encoders).

FIG. 9 illustrates a block diagram of components of a surgical systemthat includes imaging devices (e.g., C-Arm 104, O-Arm 106, etc.)connected to a computer platform 910 which can be operationallyconnected to a camera tracking system component 6 (FIG. 3A) or 6′ (FIGS.3B,3C) and/or to surgical robot 4 according to some embodiments of thepresent disclosure. Alternatively, at least some operations disclosedherein as being performed by the computer platform 910 may additionallyor alternatively be performed by components of a surgical system.

Referring to FIG. 9, the computer platform 910 includes a display 912,at least one processor circuit 914 (also referred to as a processor forbrevity), at least one memory circuit 916 (also referred to as a memoryfor brevity) containing computer readable program code 918, and at leastone network interface 902 (also referred to as a network interface forbrevity). The display 912 may be part of an XR headset 920 in accordancewith some embodiments of the present disclosure. The network interface902 can be configured to connect to a C-Arm imaging device 104 in FIG.10, an O-Arm imaging device 106 in FIG. 11, another medical imagingdevice, an image database 950 containing patient medical images,components of the surgical robot 4, and/or other electronic equipment.

When used with a surgical robot 4, the display 912 may correspond to thedisplay 34 of FIG. 2 and/or the tablet 890 of FIG. 8 and/or the XRheadset 920 that is operatively connected to the surgical robot 4, thenetwork interface 902 may correspond to the platform network interface812 of FIG. 8, and the processor 914 may correspond to the computer 822of FIG. 8. The network interface 902 of the XR headset 920 may beconfigured to communicate through a wired network, e.g., thin wireethernet, and/or through wireless RF transceiver link according to oneor more wireless communication protocols, e.g., WLAN, 3GPP 4G and/or 5G(New Radio) cellular communication standards, etc.

The processor 914 may include one or more data processing circuits, suchas a general purpose and/or special purpose processor, e.g.,microprocessor and/or digital signal processor. The processor 914 isconfigured to execute the computer readable program code 918 in thememory 916 to perform operations, which may include some or all of theoperations described herein as being performed for surgery planning,navigated surgery, and/or robotic surgery.

The computer platform 910 can be configured to provide surgery planningfunctionality. The processor 914 can operate to display on the displaydevice 912 and/or on the XR headset 920 an image of an anatomicalstructure, e.g., vertebra, that is received from one of the imagingdevices 104 and 106 and/or from the image database 950 through thenetwork interface 920. The processor 914 receives an operator'sdefinition of where the anatomical structure shown in one or more imagesis to have a surgical procedure, e.g., screw placement, such as by theoperator touch selecting locations on the display 912 for plannedprocedures or using a mouse-based cursor to define locations for plannedprocedures. When the image is displayed in the XR headset 920, the XRheadset can be configured to sense in gesture-based commands formed bythe wearer and/or sense voice based commands spoken by the wearer, whichcan be used to control selection among menu items and/or control howobjects are displayed on the XR headset 920 as will be explained infurther detail below.

The computer platform 910 can be configured to enable anatomymeasurement, which can be particularly useful for knee surgery, likemeasurement of various angles determining center of hip, center ofangles, natural landmarks (e.g. transepicondylar line, Whitesides line,posterior condylar line), etc. Some measurements can be automatic whilesome others can involve human input or assistance. The computer platform910 may be configured to allow an operator to input a choice of thecorrect implant for a patient, including choice of size and alignment.The computer platform 910 may be configured to perform automatic orsemi-automatic (involving human input) segmentation (image processing)for CT images or other medical images. The surgical plan for a patientmay be stored in a cloud-based server, which may correspond to database950, for retrieval by the surgical robot 4.

During orthopedic surgery, for example, a surgeon may choose which cutto make (e.g. posterior femur, proximal tibia etc.) using a computerscreen (e.g. touchscreen) or extended reality (XR) interaction (e.g.,hand gesture based commands and/or voice based commands) via, e.g., theXR headset 920. The computer platform 910 can generate navigationinformation which provides visual guidance to the surgeon for performingthe surgical procedure. When used with the surgical robot 4, thecomputer platform 910 can provide guidance that allows the surgicalrobot 4 to automatically move the end effector 26 to a target pose sothat the surgical tool is aligned with a target location to perform thesurgical procedure on an anatomical structure.

In some embodiments, the surgical system 900 can use two DRAs to trackpatient anatomy position, such as one connected to patient tibia and oneconnected to patient femur. The system 900 may use standard navigatedinstruments for the registration and checks (e.g. a pointer similar tothe one used in Globus ExcelsiusGPS system for spine surgery).

A particularly challenging task in navigated surgery is how to plan theposition of an implant in spine, knee, and other anatomical structureswhere surgeons struggle to perform the task on a computer screen whichis a 2D representation of the 3D anatomical structure. The system 900could address this problem by using the XR headset 920 to display athree-dimensional (3D) computer generated representations of theanatomical structure and a candidate implant device. The computergenerated representations are scaled and posed relative to each other onthe display screen under guidance of the computer platform 910 and whichcan be manipulated by a surgeon while viewed through the XR headset 920.A surgeon may, for example, manipulate the displayed computer-generatedrepresentations of the anatomical structure, the implant, a surgicaltool, etc., using hand gesture based commands and/or voice basedcommands that are sensed by the XR headset 920.

For example, a surgeon can view a displayed virtual handle on a virtualimplant, and can manipulate (e.g., grab and move) the virtual handle tomove the virtual implant to a desired pose and adjust a planned implantplacement relative to a graphical representation of an anatomicalstructure. Afterward, during surgery, the computer platform 910 coulddisplay navigation information through the XR headset 920 thatfacilitates the surgeon's ability to more accurately follow the surgicalplan to insert the implant and/or to perform another surgical procedureon the anatomical structure. When the surgical procedure involves boneremoval, the progress of bone removal, e.g., depth of cut, can bedisplayed in real-time through the XR headset 920. Other features thatmay be displayed through the XR headset 920 can include, withoutlimitation, gap or ligament balance along a range of joint motion,contact line on the implant along the range of joint motion, ligamenttension and/or laxity through color or other graphical renderings, etc.

The computer platform 910, in some embodiments, can allow planning foruse of standard surgical tools and/or implants, e.g., posteriorstabilized implants and cruciate retaining implants, cemented andcementless implants, revision systems for surgeries related to, forexample, total or partial knee and/or hip replacement and/or trauma.

An automated imaging system can be used in conjunction with the computerplatform 910 to acquire pre-operative, intra-operative, post-operative,and/or real-time image data of an anatomical structure. Exampleautomated imaging systems are illustrated in FIGS. 10 and 11. In someembodiments, the automated imaging system is a C-arm 104 (FIG. 10)imaging device or an O-arm® 106 (FIG. 11). (O-arm® is copyrighted byMedtronic Navigation, Inc. having a place of business in Louisville,Colo., USA). It may be desirable to take x-rays of a patient from anumber of different positions, without the need for frequent manualrepositioning of the patient which may be required in an x-ray system.C-arm 104 x-ray diagnostic equipment may solve the problems of frequentmanual repositioning and may be well known in the medical art ofsurgical and other interventional procedures. As illustrated in FIG. 10,a C-arm includes an elongated C-shaped member terminating in opposingdistal ends 112 of the “C” shape. C-shaped member is attached to anx-ray source 114 and an image receptor 116. The space within C-arm 104of the arm provides room for the physician to attend to the patientsubstantially free of interference from the x-ray support structure.

The C-arm is mounted to enable rotational movement of the arm in twodegrees of freedom, (i.e. about two perpendicular axes in a sphericalmotion). C-arm is slidably mounted to an x-ray support structure, whichallows orbiting rotational movement of the C-arm about its center ofcurvature, which may permit selective orientation of x-ray source 114and image receptor 116 vertically and/or horizontally. The C-arm mayalso be laterally rotatable, (i.e. in a perpendicular direction relativeto the orbiting direction to enable selectively adjustable positioningof x-ray source 114 and image receptor 116 relative to both the widthand length of the patient). Spherically rotational aspects of the C-armapparatus allow physicians to take x-rays of the patient at an optimalangle as determined with respect to the particular anatomical conditionbeing imaged.

The O-arm® 106 illustrated in FIG. 11 includes a gantry housing 124which may enclose an image capturing portion, not illustrated. The imagecapturing portion includes an x-ray source and/or emission portion andan x-ray receiving and/or image receiving portion, which may be disposedabout one hundred and eighty degrees from each other and mounted on arotor (not illustrated) relative to a track of the image capturingportion. The image capturing portion may be operable to rotate threehundred and sixty degrees during image acquisition. The image capturingportion may rotate around a central point and/or axis, allowing imagedata of the patient to be acquired from multiple directions or inmultiple planes.

The O-arm® 106 with the gantry housing 124 has a central opening forpositioning around an object to be imaged, a source of radiation that isrotatable around the interior of gantry housing 124, which may beadapted to project radiation from a plurality of different projectionangles. A detector system is adapted to detect the radiation at eachprojection angle to acquire object images from multiple projectionplanes in a quasi-simultaneous manner. The gantry may be attached to asupport structure O-arm® support structure, such as a wheeled mobilecart with wheels, in a cantilevered fashion. A positioning unittranslates and/or tilts the gantry to a planned position andorientation, preferably under control of a computerized motion controlsystem. The gantry may include a source and detector disposed oppositeone another on the gantry. The source and detector may be secured to amotorized rotor, which may rotate the source and detector around theinterior of the gantry in coordination with one another. The source maybe pulsed at multiple positions and orientations over a partial and/orfull three hundred and sixty degree rotation for multi-planar imaging ofa targeted object located inside the gantry. The gantry may furthercomprise a rail and bearing system for guiding the rotor as it rotates,which may carry the source and detector. Both and/or either O-arm® 106and C-arm 104 may be used as automated imaging system to scan a patientand send information to the surgical system 2.

Images captured by an imaging system can be displayed on the XR headset920 and/or another display device of the computer platform 910, thesurgical robot 4, and/or another component of the surgical system 900.The XR headset 920 may be connected to one or more of the imagingdevices 104 and/or 106 and/or to the image database 950, e.g., via thecomputer platform 910, to display images therefrom. A user may providecontrol inputs through the XR headset 920, e.g., gesture and/or voicebased commands, to control operation of one or more of the imagingdevices 104 and/or 106 and/or the image database 950.

FIG. 12 illustrates a block diagram view of the components of a surgicalsystem that include a pair of XR headsets 1200 and 1210 (head-mounteddisplays HMD1 and HMD2), which may correspond to the XR headset 920shown in FIG. 13 and operate in accordance with some embodiments of thepresent disclosure.

Referring to the example scenario of FIG. 12, the assistant 612 andsurgeon 610 are both wearing the XR headsets 1210 and 1210,respectively. It is optional for the assistant 612 to wear the XRheadset 1210. The XR headsets 1200 and 1210 are configured to provide aninteractive environment through which the wearers can view and interactwith information related to a surgical procedure as will be describedfurther below. This interactive XR based environment may eliminate aneed for the tech personnel 614 to be present in the operating room andmay eliminate a need for use of the display 34 shown in FIG. 6. Each XRheadset 1200 and 1210 can include one or more cameras that are beconfigured to provide an additional source of tracking of DRAs or otherreference arrays attached to instruments, an anatomical structure, theend effector 26, and/or other equipment. In the example of FIG. 12, XRheadset 1200 has a field-of-view (FOV) 1202 for tracking DRAs and otherobjects, XR headset 1210 has a FOV 1212 partially overlapping FOV 1202for tracking DRAs and other objects, and the tracking cameras 46 hasanother FOV 600 partially overlapping FOVs 1202 and 1212 for trackingDRAs and other objects.

If one or more cameras is obstructed from viewing a DRA attached to atracked object, e.g., a surgical instrument, but the DRA is in view ofone or more other cameras the tracking subsystem 830 and/or navigationcontroller 828 can continue to track the object seamlessly without lossof navigation. Additionally, if there is partial occlusion of the DRAfrom the perspective of one camera, but the entire DRA is visible viamultiple camera sources, the tracking inputs of the cameras can bemerged to continue navigation of the DRA. One of the XR headsets and/orthe tracking cameras 46 may view and track the DRA on another one of theXR headsets to enable the computer platform 910 (FIGS. 9 and 14), thetracking subsystem 830, and/or another computing component to determinethe pose of the DRA relative to one or more defined coordinate systems,e.g., of the XR headsets 1200/1210, the tracking cameras 46, and/oranother coordinate system defined for the patient, table, and/or room.

The XR headsets 1200 and 1210 can be operatively connected to viewvideo, pictures, and/or other information received from and/or toprovide commands that control various equipment in the surgical room,including but not limited to neuromonitoring, microscopes, videocameras, and anesthesia systems. Data from the various equipment may beprocessed and displayed within the headset, for example the display ofpatient vitals or the microscope feed.

Example XR Headset Components and Integration to Navigated Surgery,Surgical Robots, and Other Equipment

FIG. 13 illustrates an XR headset 920 which is configured in accordancewith some embodiments of the present disclosure. The XR headset includesa headband 1306 configured to secure the XR headset to a wearer's head,an electronic component enclosure 1304 supported by the headband 1306,and a display screen 1302 that extends laterally across and downwardfrom the electronic component enclosure 1304. The display screen 1302may be a see-through LCD display device or a semi-reflective lens thatreflects images projected by a display device toward the wearer's eyes.A set of DRA fiducials, e.g., dots are painted or attached in a spacedapart known arranged on one or both sides of the headset. The DRA on theheadset enables the tracking cameras on the auxiliary tracking bar totrack pose of the headset 920 and/or enables another XR headset to trackpose of the headset 920.

The display screen 1302 operates as a see-through display screen, alsoreferred to as a combiner, that reflects light from display panels of adisplay device toward the user's eyes. The display panels can be locatedbetween the electronic component enclosure and the user's head, andangled to project virtual content toward the display screen 1302 forreflection toward the user's eyes. The display screen 1302 issemi-transparent and semi-reflective allowing the user to see reflectedvirtual content superimposed on the user's view of a real-world scene.The display screen 1302 may have different opacity regions, such as theillustrated upper laterally band which has a higher opacity than thelower laterally band. Opacity of the display screen 1302 may beelectronically controlled to regulate how much light from the real-worldscene passes through to the user's eyes. A high opacity configuration ofthe display screen 1302 results in high-contrast virtual images overlaidon a dim view of the real-world scene. A low opacity configuration ofthe display screen 1302 can result in more faint virtual images overlaidon a clearer view of the real-world scene. The opacity may be controlledby applying an opaque material on a surface of the display screen 1302.

According to some embodiments the surgical system includes an XR headset920 and an XR headset controller, e.g., controller 1430 in FIG. 14 orcontroller 3410 in FIG. 34. The XR headset 920 is configured to be wornby a user during a surgical procedure and has a see-through displayscreen 1302 that is configured to display an XR image and to allow atleast a portion of a real-world scene to pass therethrough for viewingby the user. The XR headset 920 also includes an opacity filterpositioned between at least one of the user's eyes and the real-worldscene when the see-through display screen 1302 is viewed by the user.The opacity filter is configured to provide opaqueness to light from thereal-world scene. The XR headset controller is configured to communicatewith a navigation controller, e.g., controller(s) 828A, 828B, and/or828C in FIG. 14, to receive navigation information from the navigationcontroller which provides guidance to the user during the surgicalprocedure on an anatomical structure, and is further configured togenerate the XR image based on the navigation information for display onthe see-through display screen 1302.

Opacity of the display screen 1302 may be configured as a gradienthaving a more continuously changing opacity with distance downward froma top portion of the display screen 1302. The gradient's darkest pointcan be located at the top portion of the display screen 1302, andgradually becoming less opaque further down on the display screen 1302until the opacity is transparent or not present. In an example furtherembodiment, the gradient can change from about 90% opacity to entirelytransparent approximately at the mid-eye level of the display screen1302. With the headset properly calibrated and positioned, the mid-eyelevel can correspond to the point where the user would look straightout, and the end of the gradient would be located at the “horizon” lineof the eye. The darker portion of the gradient will allow crisp, clearvisuals of the virtual content and help to block the intrusivebrightness of the overhead operating room lights.

Using an opacity filter in this manner enables the XR headset 920 toprovide virtual reality (VR) capabilities, by substantially or entirelyblocking light from the real-world scene, along an upper portion of thedisplay screen 1302 and to provide AR capabilities along a middle orlower portion of the display screen 1302. This allows the user to havethe semi-translucence of AR where needed and allowing clear optics ofthe patient anatomy during procedures. Configuring the display screen1302 as a gradient instead of as a more constant opacity band can enablethe wearer to experience a more natural transition between a more VRtype view to a more AR type view without experiencing abrupt changes inbrightness of the real-world scene and depth of view that may otherwisestrain the eyes such as during more rapid shifting between upward anddownward views.

The display panels and display screen 1302 can be configured to providea wide field of view see-through XR display system. In one exampleconfiguration they provide an 80° diagonal field-of-view (FOV) with 55°of vertical coverage for a user to view virtual content. Other diagonalFOV angles and vertical coverage angles can be provided throughdifferent size display panels, different curvature lens, and/ordifferent distances and angular orientations between the display panelsand curved display screen 1302.

FIG. 14 illustrates electrical components of the XR headset 920 that canbe operatively connected to the computer platform 910, to one or more ofthe imaging devices, such as the C-arm imaging device 104, the O-armimaging device 106, and/or the image database 950, and/or to thesurgical robot 800 in accordance with various embodiments of the presentdisclosure.

The XR headset 920 provides an improved human interface for performingnavigated surgical procedures. The XR headset 920 can be configured toprovide functionalities, e.g., via the computer platform 910, thatinclude without limitation any one or more of: identification of handgesture based commands and/or voice based commands, display XR graphicalobjects on a display device 1450. The display device 1450 may a videoprojector, flat panel display, etc., which projects the displayed XRgraphical objects on the display screen 1302. The user can view the XRgraphical objects as an overlay anchored to particular real-worldobjects viewed through the display screen 1302 (FIG. 13). The XR headset920 may additionally or alternatively be configured to display on thedisplay screen 1450 video feeds from cameras mounted to one or more XRheadsets 920 and other cameras.

Electrical components of the XR headset 920 can include a plurality ofcameras 1440, a microphone 1442, a gesture sensor 1444, a pose sensor(e.g., inertial measurement unit (IMU)) 1446, a display module 1448containing the display device 1450, and a wireless/wired communicationinterface 1452. As will be explained below, the cameras 1440 of the XRheadset may be visible light capturing cameras, near infrared capturingcameras, or a combination of both.

The cameras 1440 may be configured operate as the gesture sensor 1444 bycapturing for identification user hand gestures performed within thefield of view of the camera(s) 1440. Alternatively the gesture sensor1444 may be a proximity sensor and/or a touch sensor that senses handgestures performed proximately to the gesture sensor 1444 and/or sensesphysical contact, e.g. tapping on the sensor or the enclosure 1304. Thepose sensor 1446, e.g., IMU, may include a multi-axis accelerometer, atilt sensor, and/or another sensor that can sense rotation and/oracceleration of the XR headset 920 along one or more defined coordinateaxes. Some or all of these electrical components may be contained in thecomponent enclosure 1304 or may be contained in another enclosureconfigured to be worn elsewhere, such as on the hip or shoulder.

As explained above, the surgical system 2 includes a camera trackingsystem component 6/6′ and a tracking subsystem 830 which may be part ofthe computer platform 910. The surgical system may include imagingdevices (e.g., C-arm 104, O-arm 106, and/or image database 950) and/or asurgical robot 4. The tracking subsystem 830 is configured to determinea pose of DRAs attached to an anatomical structure, an end effector, asurgical tool, etc. A navigation controller 828 is configured todetermine a target pose for the surgical tool relative to an anatomicalstructure based on a surgical plan, e.g., from a surgical planningfunction performed by the computer platform 910 of FIG. 9, definingwhere a surgical procedure is to be performed using the surgical tool onthe anatomical structure and based on a pose of the anatomical structuredetermined by the tracking subsystem 830. The navigation controller 828may be further configured to generate steering information based on thetarget pose for the surgical tool, the pose of the anatomical structure,and the pose of the surgical tool and/or the end effector, where thesteering information indicates where the surgical tool and/or the endeffector of a surgical robot should be moved to perform the surgicalplan.

The electrical components of the XR headset 920 can be operativelyconnected to the electrical components of the computer platform 910through a wired/wireless interface 1452. The electrical components ofthe XR headset 920 may be operatively connected, e.g., through thecomputer platform 910 or directly connected, to various imaging devices,e.g., the C-arm imaging device 104, the I/O-arm imaging device 106, theimage database 950, and/or to other medical equipment through thewired/wireless interface 1452.

The surgical system 2 further includes at least one XR headsetcontroller 1430 (also referred to as “XR headset controller” forbrevity) that may reside in the XR headset 920, the computer platform910, and/or in another system component connected via wired cablesand/or wireless communication links. Various functionality is providedby software executed by the XR headset controller 1430. The XR headsetcontroller 1430 is configured to receive navigation information from thenavigation controller 828 which provides guidance to the user during thesurgical procedure on an anatomical structure, and is configured togenerate an XR image based on the navigation information for display onthe display device 1450 for projection on the see-through display screen1302.

The configuration of the display device 1450 relative to the displayscreen (also referred to as “see-through display screen”) 1302 isconfigured to display XR images in a manner such that when the userwearing the XR headset 920 looks through the display screen 1302 the XRimages appear to be in the real world. The display screen 1302 can bepositioned by the headband 1306 in front of the user's eyes.

The XR headset controller 1430 can be within a housing that isconfigured to be worn on a user's head or elsewhere on the user's bodywhile viewing the display screen 1302 or may be remotely located fromthe user viewing the display screen 1302 while being communicativelyconnected to the display screen 1302. The XR headset controller 1430 canbe configured to operationally process signaling from the cameras 1440,the microphone 142, and/or the pose sensor 1446, and is connected todisplay XR images on the display device 1450 for user viewing on thedisplay screen 1302. Thus, the XR headset controller 1430 illustrated asa circuit block within the XR headset 920 is to be understood as beingoperationally connected to other illustrated components of the XRheadset 920 but not necessarily residing within a common housing (e.g.,the electronic component enclosure 1304 of FIG. 13) or being otherwisetransportable by the user. For example, the XR headset controller 1430may reside within the computer platform 910 which, in turn, may residewithin a housing of the computer tracking system component 6′ shown inFIGS. 3B and 3C.

Example XR Headset Component Optical Arrangement

FIG. 34 illustrates a block diagram showing arrange of opticalcomponents of the XR headset 920 in accordance with some embodiments ofthe present disclosure. Referring to FIG. 34, the display device 1450 isconfigured to display XR images generated by the XR headset controller1430, light from which is projected as XR images 1450 toward the displayscreen 1302. The display screen 1302 is configured to combine light ofthe XR images 1450 and light from the real-world scene 1502 into acombined augmented view 1504 that is directed to the user's eye(s) 1510.The display screen 1302 configured in this manner operates as asee-through display screen. The XR headset 920 can include any pluralnumber of tracking cameras 1440. The cameras 1440 may be visible lightcapturing cameras, near infrared capturing cameras, or a combination ofboth.

Example User Views Through the XR Headset

The XR headset operations can display both 2D images and 3D models onthe display screen 1302. The 2D images may preferably be displayed in amore opaque band of the display screen 1302 (upper band) and the 3Dmodel may be more preferably displayed in the more transparent band ofthe display screen 1302, otherwise known as the environmental region(bottom band). Below the lower band where the display screen 1302 endsthe wearer has an unobstructed view of the surgical room. It is notedthat where XR content is display on the display screen 1302 may befluidic. It is possible that where the 3D content is displayed moves tothe opaque band depending on the position of the headset relative to thecontent, and where 2D content is displayed can be placed in thetransparent band and stabilized to the real world. Additionally, theentire display screen 1302 may be darkened under electronic control toconvert the headset into virtual reality for surgical planning orcompletely transparent during the medical procedure. As explained above,the XR headset 920 and associated operations not only support navigatedprocedures, but also can be performed in conjunction with roboticallyassisted procedures.

FIG. 16 illustrates an example view through the display screen 1302 ofthe XR headset 920 for providing navigation assistance to a user who ismanipulating a surgical tool 1602 during a medical procedure inaccordance with some embodiments of the present disclosure. Referring toFIG. 16, when the surgical tool 1602 is brought in vicinity of a trackedanatomical structure so that dynamic reference arrays 1630 and 1632,connected to the surgical tool 1602, become within the field of view ofthe cameras 1440 (FIG. 15) and/or 46 (FIG. 6), a graphicalrepresentation 1600 of the tool can be displayed in 2D and/or 3D imagesin relation to a graphical representation 1610 of the anatomicalstructure. The user can use the viewed graphical representations toadjust a trajectory 1620 of the surgical tool 1602, which can beillustrated as extending from the graphical representation 2000 of thetool through the graphical representation 1610 of the anatomicalstructure. The XR headset 920 may also display textual information andother objects 1640. The dashed line 1650 extending across the vieweddisplay screen represents an example division between different opacitylevel upper and lower bands.

Other types of XR images (virtual content) that can be displayed on thedisplay screen 1302 can include, but are not limited to any one or moreof:

-   -   I) 2D Axial, Sagittal and/or Coronal views of patient anatomy;    -   2) overlay of planned vs currently tracked tool and surgical        implant locations;    -   3) gallery of preoperative images;    -   4) video feeds from microscopes and other similar systems or        remote video conferencing;    -   5) options and configuration settings and buttons;    -   6) floating 3D models of patient anatomy with surgical planning        information;    -   7) real-time tracking of surgical instruments relative to        floating patient anatomy;    -   8) augmented overlay of patient anatomy with instructions and        guidance; and    -   9) augmented overlay of surgical equipment.

Example Configuration of Cameras for Tracking System Component

FIG. 17 illustrates example configuration of an auxiliary tracking bar46 having two pairs of stereo tracking cameras configured in accordancewith some embodiments of the present disclosure. The auxiliary trackingbar 46 is part of the camera tracking system component of FIGS. 3A, 3B,and 3C. The stereo tracking cameras include a stereo pair of spacedapart visible light capturing cameras and another stereo pair of spacedapart near infrared capturing cameras, in accordance with oneembodiment. Alternatively, only one stereo pair of visible lightcapturing cameras or only one stereo pair of near infrared capturecameras can used in the auxiliary tracking bar 46. Any plural number ofnear infrared and/or visible light cameras can be used.

Pose Measurement Chaining

As explained above, navigated surgery can include computer visiontracking and determination of pose (e.g., position and orientation in asix degree-of-freedom coordinate system) of surgical instruments, suchas by determining pose of attached DRAs that include spaced apartfiducials, e.g., disks or spheres, arranged in a known manner. Thecomputer vision uses spaced apart tracking cameras, e.g., stereocameras, that are configured to capture near infrared and/or visiblelight. In this scenario, there are three parameters jointly competingfor optimization: (1) accuracy, (2) robustness, and (3) user ergonomicsduring a surgical procedure.

Some further aspects of the present disclosure are directed to computeroperations that combine (chain) measured poses in ways that can improveoptimization of one or more of the above three parameters byincorporating additional tracking cameras mounted to one or more XRheadsets. As shown in FIG. 17, a stereo pair of visible light trackingcameras and another stereo pair of near infrared tracking cameras can beattached to the auxiliary tracking bar of the camera tracking systemcomponent in accordance with some embodiments of the present disclosure.Operational algorithms are disclosed that analyze the pose of DRAs thatare fully observed or partially observed (e.g., when less than all ofthe fiducials of a DRA are viewed by a pair of stereo cameras), andcombine the observed poses or partial poses in ways that can improveaccuracy, robustness, and/or ergonomics during navigated surgery.

As explained above, the XR headset may be configured to augment areal-world scene with computer generated XR images. The XR headset maybe configured to provide an XR viewing environment by displaying thecomputer generated XR images on a see-through display screen that allowslight from the real-world scene to pass therethrough for combinedviewing by the user. Alternatively, the XR headset may be configured toprovide a VR viewing environment by preventing or substantiallypreventing light from the real-world scene from being directly viewed bythe user along the viewing path of the displayed XR images. An XRheadset can be configured to provide both AR and VR viewingenvironments. In one embodiment, both AR and VR viewing environments areprovided by lateral bands of substantially differing opacity arrangedbetween the see-through display screen and the real-world scene, so thata VR viewing environment is provided for XR images aligned with a highopacity band and an AR viewing environment is provided for XR imagesaligned with the low opacity band. In another embodiment, both AR and VRviewing environments are provided by computer adjustable control of anopacity filter that variably constrains how much light from thereal-world scene passes through a see-through display screen forcombining with the XR images viewed by the user. Thus, the XR headsetcan also be referred to as an AR headset or a VR headset.

As was also explained above, the XR headset can include near infraredtracking cameras and/or visible light tracking cameras that areconfigured to track fiducials of DRAs connected to surgical instruments,patient anatomy, other XR headset(s), and/or a robotic end effector.Using near infrared tracking and/or visible light tracking on the XRheadset provides additional tracking volume coverage beyond what camerason a single auxiliary tracking bar can provide. Adding near infraredtracking cameras to the existing auxiliary tracking bar allows for theheadset location to be tracked more robustly but less accurately than invisible light. Mechanically calibrating the visible and near infraredtracking coordinate systems enables the coordinate systems to be alignedsufficiently to perform 3D DRA fiducials triangulation operations usingstereo matching to jointly identify pose of the DRA fiducials betweenthe visible and near infrared tracking coordinate systems. Using bothvisible and near infrared tracking coordinate systems can enable any oneor more of: (a) identifying tools that would not be identified using asingle coordinate system; (b) increased pose tracking accuracy; (c)enabling a wider range of motion without losing tracking of surgicalinstruments, patient anatomy, and/or a robotic end effector; and (d)naturally track an XR headset in the same coordinate system as thenavigated surgical instruments.

FIG. 18 illustrates a block diagram view of the components of a surgicalsystem that include tracking cameras in a pair of XR headsets 1200 and1210 (head-mounted displays HMD1 and HMD2) and tracking cameras in acamera tracking bar in the camera tracking system component 6′ whichhouses the computer platform 910. The computer platform 910 can includethe tracking subsystem 830, the navigation controller 828, and the XRheadset controller 1430 as was earlier shown in FIG. 14.

Referring to the surgical system of FIG. 18, a surgeon and an assistantare both wearing XR headsets HMD1 1200 and HMD2 1210, respectively, eachif which includes tracking cameras that may be configured as shown inFIG. 13. It is optional for the assistant to wear the XR headset HMD21210.

The combination of XR headsets HMD1 1200 and HMD2 1210 and the trackingcameras 46 on the auxiliary tracking bar can, in operation with thecomputer platform 910, more robustly track the example objects of apatient reference array (R), robotic end effector (E), and surgical tool(T) or instrument. The overlapping views from different perspectivesthat are provided by the XR headsets HMD1 1200 and HMD2 1210 and thetracking cameras 46 on the auxiliary tracking bar are shown in FIG. 12.

Each of the items labeled in FIG. 18 represent a unique coordinatesystem. Descriptions of the coordinate system labels are as follows:

-   -   A=visible light coordinate system of second headset HMD2 1210;    -   N3=NIR coordinate system of second headset HMD2 1210;    -   S=visible light coordinate system of primary headset HMD1 1200;    -   N2=NIR coordinate system of the primary headset HMD1 1200;    -   N=NIR coordinate system of the auxiliary navigation bar 46;    -   V=visible light coordinate system of the auxiliary navigation        bar 46;    -   R=NIR coordinate system of a patient reference fiducial array        602;    -   T=NIR coordinate system of a tracked tool 604;    -   E=NIR coordinate system of a tracked robot end effector on        robotic arm 20; and    -   W=Inertially navigated world coordinate system with stable        gravity vector.

The spatial relationships of some of these labeled objects (and byextension, coordinate systems) can be measured and calibrated during themanufacturing process, when the equipment is installed in an operatingroom, and/or before a surgical procedure is to be performed. In thedisclosed system, the following coordinate systems are calibrated:T_(N2) ^(S); T_(N3) ^(A); T_(N) ^(V), where the term “T” is defined as asix degree-of-freedom (6 DOF) homogeneous transformation between the twoindicated coordinates systems. Thus, for example, the term T_(N2) ^(S)is a 6 DOF homogeneous transformation between the visible lightcoordinate system of the primary headset HMD1 1200 and the NIRcoordinate system of the primary headset HMD1 1200.

In one embodiment, the XR headsets HMD1 1200 and HMD2 1210 have passivevisible light markers painted or otherwise attached to them (coordinatesystems S and A), such as the DRA fiducials 1310 shown in FIG. 13. Thetracking cameras are spatially calibrated to these passive fiducials(coordinate systems N2 and N3).

As explained above, the cameras on the XR headset HMD1 1200 and HMD21210 and the tracking cameras 46 on the auxiliary tracking bar havepartially overlapping field of views. If one or more of the cameras onthe XR headset HMD1 1200 are obstructed from viewing a DRA attached to atracked object, e.g., a tracked tool (T), but the DRA is in view of thecameras of the other XR headset HMD2 1210 and/or the tracking cameras 46on the auxiliary tracking bar, the computer platform 910 can continue totrack the DRA seamlessly without loss of navigation. Additionally, ifthere is partial occlusion of the DRA from the perspective of thecameras on the XR headset HMD1 1200, but the entire DRA is visible viacameras of the other XR headset HMD2 1210 and/or the tracking cameras 46on the auxiliary tracking bar, the tracking inputs of the cameras can bemerged to continue navigation of the DRA.

More particularly, the various coordinate systems can be chainedtogether by virtue of independent observations the various camerasystems provided by the XR headsets HMD1 1200 and HMD2 1210 and thetracking cameras 46 on the auxiliary tracking bar. For example, each ofthe XR headsets HMD1 1200 and HMD2 1210 may require virtual augmentationof the robotic end effector (E). While one XR headset HMD1 1200 (N2) andthe tracking cameras 46 on the auxiliary tracking bar (N) are able tosee (E), perhaps the other XR headset HMD2 1210 (N3) cannot. Thelocation of (E) with respect to (N3) can still be computed via one ofseveral different operational methods. Operations according to oneembodiment performing chaining of poses from a patient reference (R). Ifthe patient reference (R) is seen by (N3) and either one of (N) or (N2),the pose of (E) with respect to (N3) can be solved directly by eitherone of the following two equations:

T_(N3) ^(E)=T_(N2) ^(E)T_(R) ^(N2)T_(N3) ^(R) -or- T_(N3) ^(E)=T_(N)^(E)T_(R) ^(N)T_(N3) ^(R)

They key to this pose chaining is that the relationship between theframes at the end of each chain are inferred (circled and transportedbelow). The chains can be arbitrarily long and are enabled by havingmore than one stereo camera system (e.g., N, N2, N3).

The camera tracking system can be configured to receive trackinginformation related to tracked objects from a first tracking camera(e.g., N3) and a second tracking camera (e.g., N2) during a surgicalprocedure. The camera tracking system can determine a first posetransform (e. g., T_(N3) ^(R)) between a first object (e.g., R)coordinate system and the first tracking camera (e.g., N3) coordinatesystem based on first object tracking information from the firsttracking camera (e.g., N3) which indicates pose of the first object(e.g., R). The camera tracking system can determine a second posetransform (e.g., T_(R) ^(N2)) between the first object (e.g., R)coordinate system and the second tracking camera (e.g., N2) coordinatesystem based on first object tracking information from the secondtracking camera (e.g., N2) which indicates pose of the first object(e.g., R). The camera tracking system can determine a third posetransform (e.g., T_(N2) ^(E)) between a second object (e.g., E)coordinate system and the second tracking camera (e.g., N2) coordinatesystem based on second object tracking information from the secondtracking camera (e.g., N2) which indicates pose of the second object(e.g., E). The camera tracking system can determine a fourth posetransform (e.g., T_(N3) ^(E)) between the second object (e.g., E)coordinate system and the first tracking camera (e.g., N3) coordinatesystem based on combining the first, second, and third pose transforms.

In some further embodiments, the camera system can further determinepose of the second object (e.g., E) and the first tracking camera system(e.g., N3) coordinate system based on processing the trackinginformation through the fourth pose transform.

Because of the overlapping field of views of the various camera systems,the camera tracking system is capable of determining the pose of thesecond object (e.g., E) relative to first tracking camera (e.g., N3)when the first camera is blocked from seeing the second object (e.g.,E). For example, in some embodiments the camera tracking system isfurther configured to determine the fourth pose transform (e.g., T_(N3)^(E)) between the second object (e.g., E) coordinate system and thefirst tracking camera (e.g., N3) coordinate system without use of anytracking information from the first tracking camera (e.g., N3)indicating pose of the second object (e.g., E).

The camera tracking system can be further configured to determine poseof the second object (e.g., E) in the first tracking camera (e.g., N3)coordinate system based on processing through the fourth pose transformthe tracking information from the first tracking camera (e.g., N3) whichindicates pose of the first object (e.g., R), based on processingthrough the fourth pose transform (e.g., T_(N3) ^(E)) the trackinginformation from the second tracking camera (e.g., N2) which indicatespose of the first object (e.g., R), and based on processing through thefourth pose transform the tracking information from the second trackingcamera (e.g., N2) which indicates pose of the second object (e.g., E).

Eye Tracking Using Inside-Out Cameras

In accordance with various further embodiments of the disclosure, an XRheadset includes stereo tracking cameras used for inside-out tracking.The stereo tracking cameras are used to track the user's eyes andcalibrate the headset to the eyes' (e.g., pupils') positions if thereare two users facing each other or if a reflective surface is present.

Eye tracking systems normally use one to two inward facing cameras pereye to track where the eyes of a user wearing an XR headset are locatedand where the eyes are looking. In some embodiments, the eyes aretracked by their shape directly in visible light.

FIG. 19 illustrates an embodiment in which two users wearing XR headsetsare facing each other and the camera tracking system uses the stereotracking cameras on each XR headset to track the other user's eyes.

FIG. 22 illustrates a flow chart of operations performed by a cameratracking system for calibrating eye-to-XR headset displays andresponsively controlling where symbols are displayed on XR headsets inaccordance with some embodiments.

Referring to FIGS. 19 and 22, a camera tracking system operativelydetermines 2200 a first pose of a second extended-reality (XR) headset1910 relative to stereo tracking cameras 1902 located on a first XRheadset 1900 based on first tracking information from the stereotracking cameras 1902. The camera tracking system determines 2202 asecond pose of eyes of a user 1920 wearing the second XR headset 1910relative to the stereo tracking cameras 1902 located on the first XRheadset 1900 based on second tracking information from the stereotracking cameras 1902. The camera tracking system also calibrates 2206an eye-to-display relationship defining pose of the eyes 1914 of theuser 1920 wearing the second XR headset 1910 to a display device of thesecond XR headset 1910 based on the determined first and second poses.The camera tracking system also controls 2208 where symbols aredisplayed on the display device of the second XR headset 1910 based onthe eye-to-display relationship. This XR headset embodiment allows thetracking cameras 1902 on the first XR headset 1900 to track the pose ofthe second XR headset 1910 and the eyes 1914 of the user 1920 directly.

FIG. 24 illustrates a flow chart of operations performed by the cameratracking system for calibrating eye-to-XR headset displays of the otheruser (e.g. the user wearing the first XR headset) and responsivelycontrolling where symbols are displayed on XR headsets in accordancewith some embodiments.

Referring to FIG. 24, in a similar manner, the stereo tracking cameras1912 on the second XR headset 1910 can be used to calibrate theeye-to-display relationship between the eyes 1904 of the user 1930wearing the first XR headset 1900. More particularly, the cameratracking system operatively determines 2400 a third pose of a first XRheadset 1900 relative to the stereo tracking cameras 1912 located on thesecond XR headset 1910 based on third tracking information from thestereo tracking cameras 1912. The camera tracking system determines 2402a fourth pose of eyes 1904 of the user 1930 wearing the first XR headset1900 relative to the stereo tracking cameras 1912 located on the secondXR headset 1910 based on fourth tracking information from the stereotracking cameras 1912. The camera tracking system also calibrates 2404an eye-to-display relationship defining pose of the eyes 1904 of theuser 1930 wearing the first XR headset 1900 to a display device of thefirst XR headset 1900 based on the determined third and fourth poses.The camera tracking system also controls 2206 where symbols aredisplayed on the display device of the first XR headset 1900 based onthe eye-to-display relationship. This XR headset embodiment allows thetracking cameras 1912 on the second XR headset 1910 to track the pose ofthe first XR headset 1900 and the eyes 1904 of the user 1930 directly.

Some other embodiments include tracking markers located on the XRheadset in order to improve robustness of headset pose estimation. Insome embodiments, the first tracking information from the stereotracking cameras 1902 on the first XR headset 1900 tracks a referencearray on the second XR headset 1910. The second tracking informationfrom the stereo tracking cameras 1902 tracks the eyes 1914 of the userwearing the second XR headset 1910. The XR headset-to-display transformrelates the pose of the reference array on the second XR headset 1910and the pose of the display device of the second XR headset 1910.

In some other embodiments, the determination of the first pose of thesecond XR headset 1910 relative to the stereo tracking cameras locatedon the first XR headset 1900, includes to determine first offsetdistances between the stereo tracking cameras 1902 located on the firstXR headset 1900 and the second XR headset 1910. The determination of thesecond pose of the eyes 1914 of the user 1920 wearing the second XRheadset 1910 relative to the stereo tracking cameras 1902 located on thefirst XR headset 1900, includes to determine second offset distancesbetween the stereo tracking cameras 1902 located on the first XR headset1900 and the eyes 1914 of the user 1920. The calibration of theeye-to-display relationship defining pose of the eyes 1914 of the user1920 wearing the second XR headset 1910 to the display device of thesecond XR headset 1910, includes to determine third offset distancesbetween the eyes 1914 of the user 1920 and the display device of thesecond XR headset 1910 based on the first and second offset distances.

Continuous tracking of the eyes 1914 of the user 1920 may thereby beachieved when there are two users 1920 and 1930 facing each other whilerespectively wearing the two headsets 1900 and 1910. The outward facingstereo tracking cameras 1902 will be able to track the other headset'spose as well as the other user's eyes 1914 relative to the headset beingworn (while the two users are facing each other). One example of wherethis would happen regularly is in a surgery. A surgeon and a surgicalassistant normally stand across the table from each other and face eachother. If both are wearing headsets, the camera tracking system would beable to repetitively or continuously track the both person's headset andeyes.

In some embodiments, the determination of the second pose and thecalibration of the eye-to-display relationship are performed responsiveto detection of the eyes 1914 of the user 1920 wearing the second XRheadset 1910 when imaged in video frames from the stereo trackingcameras 1902 located on the first XR headset 1900.

Accuracy of the pose determination from dynamic head tracking can beimproved by time synchronizing the video streams between the stereotracking cameras 1902 and 1912 on the respective XR headsets 1900 and1910. The camera tracking system 910 can perform time synchronization ofthe video streams in several different embodiments. In one embodiment,each XR headset provides a synchronization signal which is used by thecamera tracking system 910 to synchronize the video streams for purposesof object tracking. The synchronization signal may be transmittedthrough a wired or wireless connection with the video frames. The cameratracking system 910 may use the synchronization signals to estimate thetime offset between the stereo tracking cameras 1902 and 1912 on therespective XR headsets 1900 and 1910. In another embodiments, the XRheadsets 1900 and 1910 include a forward-facing light emitter apparatus(e.g., photo-diode/LED). The camera tracking system 910 can determinetime offset between the stereo tracking cameras 1902 and 1912 based ontime offset observed between when the light occurs the video frames.When determining pose of the XR headsets 1900 and 1910 and the user'seyes, the camera tracking system 910 can time align the video streamsfrom the respective stereo tracking cameras 1902 and 1912 to compensatefor the determined time offset between the video streams.

FIG. 20 illustrates an embodiment of one user 2010 wearing an XR headset2000 who's eyes 2004 are tracking using reflections from a reflectivesurface 2020 that are imaged in video frames from the stereo trackingcameras 2002, in accordance with some embodiments of the presentdisclosure. Referring to FIG. 20, when the XR headset 2000 has outwardfacing stereo tracking cameras 2002 and trackable headset shape/form andis faced toward a reflective surface 2020, the stereo tracking cameras2002 can then image the user's eyes 2004 as well as the headset'sapparent shape (i.e. pose). An outside-in tracking setup such as thisallows the cameras 2002 to determine how far away the user 2010 is fromthe reflective surface 2020 and how far the user's eyes 2004 are fromthe cameras 2002 and the headset 2000 itself. This set up also enablesthe camera tracking system 910 to estimate the eyes (e.g., pupils) posesin space relative to the headset 2000. With this information, the systemwill be able to render content with less warping and the user 2010 mayneed to spend less time adjusting the headset 2000 to avoid sharpnessdegradation in displayed objects and/or degradation in alignmentaccuracy between where displayed objects are overlaid on trackedreal-world objects. These operations enable the camera tracking system910 to compensate for when the headset 2000 shifts on the user's head,but in the case of using imaging from the reflectively surface 2020,only while the user is looking at the reflective surface 2020.

In some embodiments, the second XR headset 2000 is a reflected imagefrom a reflective surface 2020 of the first XR headset 2000 imaged invideo frames from the stereo tracking cameras 2002 located on the firstXR headset 2000.

These above embodiments allow for eye tracking without the need of anadditional tracking system if the headset has an inside-out trackingsystem and can see a reflective surface which reflects images of theheadset and the user's eyes or can see another headset and the eyes ofthe user wearing the other headset.

FIG. 21 illustrates an embodiment of tracking coordinate systems for twoXR headsets 2100 and 2110 in accordance with some embodiments of thepresent disclosure. All the optical recognition, tracking and poseestimation are performed by and relative to stereo cameras “CA” and“CB”. The translation and orientation relationships between the trackingcameras and headset (or headset marker) coordinate systems (T_(HA) ^(CA)and T_(HB) ^(CB)) may be calibrated in the factory or during asubsequent calibration process as may be the camera to displayrelationships (T_(DA) ^(CA) and T_(DB) ^(CB)). A potential advantage ofapplying these translation and orientation relationships between thetracking cameras and headset is that improved calibration ofeye-to-display relationships can be dynamically performed and resultingimprovements for where symbols are displayed on the display devices ofthe XR headsets may be obtained during navigated surgery.

Referring to FIG. 22, in some embodiments, the camera tracking system isfurther configured to operatively obtain 2204 an XR headset-to-displaytransform between a pose of the second XR headset and a pose of thedisplay device of the second XR headset. The determination of the secondpose of the eyes of the user wearing the second XR headset relative tothe stereo tracking cameras located on the first XR headset is performedbased on the second tracking information from the stereo trackingcameras located on the first XR headset and the XR headset-to-displaytransform.

In order for eye tracking to inform improved eye to display calibrationand de-warping (T_(EA) ^(DA) and T_(EB) ^(DB)), the tracking camerasshould be able to recognize and localize both a set of eyes and thecorresponding headset coordinate systems in the same optical frames.

In some embodiments, the control of where information is displayed onthe display device of the second XR headset based on the eye-to-displayrelationship, includes to adjust a projected image displayed on asee-through display screen of the display device of the second XRheadset based on the eye-to-display relationship.

Significant “real-world” distortion through the displays (i.e.,refraction) would add another level of complexity to properly localizingthe eyes. If such distortion existed, it would advantageously becompensated for via real-world display calibration in the factory. Suchcalibration would be applied in the context of the tracked camera todisplay relationships (T_(DB) ^(CA) and T_(DA) ^(CB)).

FIG. 23 illustrates a flow chart of operations performed by a cameratracking system in accordance with some embodiments.

Referring to FIG. 23, in some embodiments the camera tracking system isfurther configured to operatively obtain 2300 a display-to-eyedistortion transform relating optical distortion of real-world imagespassing through the see-through display screen of the display device ofthe second XR headset to where a wearer's eyes are posed relative to thesee-through display screen. The camera tracking system is also furtherconfigured to operatively further control 2302 where symbols aredisplayed on the see-through display screen of the display device of thesecond XR headset based on the eye-to-display relationship and thedisplay-to-eye distortion transform.

In some embodiments, recalibration is initiated to ensure accuracy ofthe displayed images by the XR headset. In one embodiment, the cameratracking system is further configured to operatively display a prompt onthe display device of the second XR headset indicating that the usershould look at the first XR headset responsive to expiration of athreshold recalibration time since a last calibration of theeye-to-display relationship was performed. In another embodiment, thecamera tracking system is further configured to operatively display aprompt on the display device of the second XR headset indicating thatthe user should adjust pose of the second XR headset relative to theeyes of the user responsive to determining the second XR headset hasshifted more than a threshold amount relative to the eyes of the userwearing the second XR headset.

Some other embodiments relate to the tracking of one headset to another(T_(HA) ^(HB)) via the tracking cameras. It may be the case that oneheadset tracking cameras are obstructed or not properly tracking in thesame shared (multi-user) coordinate system. In such a situation, theability for one headset to directly track the pose of another headsetwould enable improved shared AR experiences.

As explained above, In some embodiments, the second XR headset is usedto perform inside-out eye tracking of the first XR headset wearer.Referring to FIG. 19, in these embodiments, the camera tracking systemis further configured to operatively determine a third pose of the firstXR headset 1900 relative to second stereo tracking cameras located onthe second XR headset based on third tracking information from thesecond stereo tracking cameras. The camera tracking system is alsofurther configured to operatively determine a fourth pose of eyes of auser wearing the first XR headset relative to the second stereo trackingcameras located on the second XR headset based on fourth trackinginformation from the second stereo tracking cameras. The camera trackingsystem is also further configured to operatively calibrate aneye-to-display relationship defining pose of the eyes of the userwearing the first XR headset to the display device of the first XRheadset based on the determined third and fourth poses. The cameratracking system is also further configured to operatively control wheresymbols are displayed on the display device of the first XR headsetbased on the eye-to-display relationship.

The following embodiments relate to a computer program product includingprogram code executable by the camera tracking system similar toembodiments discussed above.

In various embodiments, a computer program product comprising anon-transitory computer readable medium storing program code executableby a camera tracking system is operative to determine a first pose ofthe second XR headset relative to stereo tracking cameras located on thefirst XR headset based on first tracking information from the stereotracking cameras. The program code executable by the camera trackingsystem is operative to also determine a second pose of eyes of a userwearing the second XR headset relative to the stereo tracking cameraslocated on the first XR headset based on second tracking informationfrom the stereo tracking cameras. The program code executable by thecamera tracking system is operative to also calibrate an eye-to-displayrelationship defining pose of the eyes of the user wearing the second XRheadset to a display device of the second XR headset based on thedetermined first and second poses. The program code executable by thecamera tracking system is operative to also control where symbols aredisplayed on the display device of the second XR headset based on theeye-to-display relationship.

In some embodiments, the program code executable by the camera trackingsystem is further operative to obtain an XR headset-to-display transformbetween a pose of the second XR headset and a pose of the display deviceof the second XR headset. The determination of the second pose of theeyes of the user wearing the second XR headset relative to the stereotracking cameras located on the first XR headset is performed based onthe second tracking information from the stereo tracking cameras locatedon the first XR headset and the XR headset-to-display transform.

In some embodiments, the first tracking information from the stereotracking cameras tracks a reference array on the second XR headset. Thesecond tracking information from the stereo tracking cameras tracks theeyes of the user wearing the second XR headset. The XRheadset-to-display transform relates the pose of the reference array onthe second XR headset and the pose of the display device of the secondXR headset.

In some embodiments, the determination of the first pose of the secondXR headset relative to the stereo tracking cameras located on the firstXR headset, includes to determine first offset distances between thestereo tracking cameras located on the first XR headset and the secondXR headset. The determination of the second pose of the eyes of the userwearing the second XR headset relative to the stereo tracking cameraslocated on the first XR headset, includes to determine second offsetdistances between the stereo tracking cameras located on the first XRheadset and the eyes of the user. The calibration of the eye-to-displayrelationship defining pose of the eyes of the user wearing the second XRheadset to the display device of the second XR headset, includes todetermine third offset distances between the eyes of the user and thedisplay device of the second XR headset based on the first and secondoffset distances.

In some embodiments, the determination of the second pose and thecalibration of the eye-to-display relationship are performed responsiveto detection of the eyes of the user wearing the second XR headset whenimaged in video frames from the stereo tracking cameras located on thefirst XR headset.

In some embodiments, the control of where information is displayed onthe display device of the second XR headset based on the eye-to-displayrelationship, includes to adjust a projected image displayed on asee-through display screen of the display device of the second XRheadset based on the eye-to-display relationship.

In some embodiments, the program code executable by the camera trackingsystem is further operative to obtain a display-to-eye distortiontransform relating optical distortion of real-world images passingthrough the see-through display screen of the display device of thesecond XR headset to where a wearer's eyes are posed relative to thesee-through display screen. The program code executable by the cameratracking system is also further operative to further control wheresymbols are displayed on the see-through display screen of the displaydevice of the second XR headset based on the eye-to-display relationshipand the display-to-eye distortion transform.

In some embodiments, the program code executable by the camera trackingsystem is further operative to, responsive to expiration of a thresholdrecalibration time since a last calibration of the eye-to-displayrelationship was performed, displaying a prompt on the display device ofthe second XR headset indicating that the user should look at the firstXR headset.

In some embodiments, the program code executable by the camera trackingsystem is further operative to, responsive to determining the second XRheadset has shifted more than a threshold amount relative to the eyes ofthe user wearing the second XR headset, displaying a prompt on thedisplay device of the second XR headset indicating that the user shouldadjust pose of the second XR headset relative to the eyes of the user.

In some embodiments, the program code executable by the camera trackingsystem is further operative to determine a third pose of the first XRheadset relative to second stereo tracking cameras located on the secondXR headset based on third tracking information from the second stereotracking cameras. The program code executable by the camera trackingsystem is also further operative to determine a fourth pose of eyes of auser wearing the first XR headset relative to the second stereo trackingcameras located on the second XR headset based on fourth trackinginformation from the second stereo tracking cameras. The program codeexecutable by the camera tracking system is also further operative tocalibrate an eye-to-display relationship defining pose of the eyes ofthe user wearing the first XR headset to the display device of the firstXR headset based on the determined third and fourth pose. The programcode executable by the camera tracking system is also further operativeto control where symbols are displayed on the display device of thefirst XR headset based on the eye-to-display relationship.

Further Definitions and Embodiments

In the above-description of various embodiments of present inventiveconcepts, it is to be understood that the terminology used herein is forthe purpose of describing particular embodiments only and is notintended to be limiting of present inventive concepts. Unless otherwisedefined, all terms (including technical and scientific terms) usedherein have the same meaning as commonly understood by one of ordinaryskill in the art to which present inventive concepts belongs. It will befurther understood that terms, such as those defined in commonly useddictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of this specification andthe relevant art and will not be interpreted in an idealized or overlyformal sense expressly so defined herein.

When an element is referred to as being “connected”, “coupled”,“responsive”, or variants thereof to another element, it can be directlyconnected, coupled, or responsive to the other element or interveningelements may be present. In contrast, when an element is referred to asbeing “directly connected”, “directly coupled”, “directly responsive”,or variants thereof to another element, there are no interveningelements present. Like numbers refer to like elements throughout.Furthermore, “coupled”, “connected”, “responsive”, or variants thereofas used herein may include wirelessly coupled, connected, or responsive.As used herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. Well-known functions or constructions may not be described indetail for brevity and/or clarity. The term “and/or” includes any andall combinations of one or more of the associated listed items.

It will be understood that although the terms first, second, third, etc.may be used herein to describe various elements/operations, theseelements/operations should not be limited by these terms. These termsare only used to distinguish one element/operation from anotherelement/operation. Thus, a first element/operation in some embodimentscould be termed a second element/operation in other embodiments withoutdeparting from the teachings of present inventive concepts. The samereference numerals or the same reference designators denote the same orsimilar elements throughout the specification.

As used herein, the terms “comprise”, “comprising”, “comprises”,“include”, “including”, “includes”, “have”, “has”, “having”, or variantsthereof are open-ended, and include one or more stated features,integers, elements, steps, components or functions but does not precludethe presence or addition of one or more other features, integers,elements, steps, components, functions or groups thereof. Furthermore,as used herein, the common abbreviation “e.g.”, which derives from theLatin phrase “exempli gratia,” may be used to introduce or specify ageneral example or examples of a previously mentioned item, and is notintended to be limiting of such item. The common abbreviation “i.e.”,which derives from the Latin phrase “id est,” may be used to specify aparticular item from a more general recitation.

Example embodiments are described herein with reference to blockdiagrams and/or flowchart illustrations of computer-implemented methods,apparatus (systems and/or devices) and/or computer program products. Itis understood that a block of the block diagrams and/or flowchartillustrations, and combinations of blocks in the block diagrams and/orflowchart illustrations, can be implemented by computer programinstructions that are performed by one or more computer circuits. Thesecomputer program instructions may be provided to a processor circuit ofa general purpose computer circuit, special purpose computer circuit,and/or other programmable data processing circuit to produce a machine,such that the instructions, which execute via the processor of thecomputer and/or other programmable data processing apparatus, transformand control transistors, values stored in memory locations, and otherhardware components within such circuitry to implement thefunctions/acts specified in the block diagrams and/or flowchart block orblocks, and thereby create means (functionality) and/or structure forimplementing the functions/acts specified in the block diagrams and/orflowchart block(s).

These computer program instructions may also be stored in a tangiblecomputer-readable medium that can direct a computer or otherprogrammable data processing apparatus to function in a particularmanner, such that the instructions stored in the computer-readablemedium produce an article of manufacture including instructions whichimplement the functions/acts specified in the block diagrams and/orflowchart block or blocks. Accordingly, embodiments of present inventiveconcepts may be embodied in hardware and/or in software (includingfirmware, resident software, micro-code, etc.) that runs on a processorsuch as a digital signal processor, which may collectively be referredto as “circuitry,” “a module” or variants thereof.

It should also be noted that in some alternate implementations, thefunctions/acts noted in the blocks may occur out of the order noted inthe flowcharts. For example, two blocks shown in succession may in factbe executed substantially concurrently or the blocks may sometimes beexecuted in the reverse order, depending upon the functionality/actsinvolved. Moreover, the functionality of a given block of the flowchartsand/or block diagrams may be separated into multiple blocks and/or thefunctionality of two or more blocks of the flowcharts and/or blockdiagrams may be at least partially integrated. Finally, other blocks maybe added/inserted between the blocks that are illustrated, and/orblocks/operations may be omitted without departing from the scope ofinventive concepts. Moreover, although some of the diagrams includearrows on communication paths to show a primary direction ofcommunication, it is to be understood that communication may occur inthe opposite direction to the depicted arrows.

Many variations and modifications can be made to the embodiments withoutsubstantially departing from the principles of the present inventiveconcepts. All such variations and modifications are intended to beincluded herein within the scope of present inventive concepts.Accordingly, the above disclosed subject matter is to be consideredillustrative, and not restrictive, and the appended examples ofembodiments are intended to cover all such modifications, enhancements,and other embodiments, which fall within the spirit and scope of presentinventive concepts. Thus, to the maximum extent allowed by law, thescope of present inventive concepts are to be determined by the broadestpermissible interpretation of the present disclosure including thefollowing examples of embodiments and their equivalents, and shall notbe restricted or limited by the foregoing detailed description.

What is claimed is:
 1. A method of computer assisted navigation duringsurgery comprising: receiving, from a reflective surface, a reflectionof an extended-reality (XR) headset by stereo cameras of the XR headset,the XR headset having a see-through screen for displaying images forviewing by a user wearing the XR headset; determining a pose of the usereyes relative to the XR headset based on the received reflection;calibrating an eye-to-display relationship based on the determined poseof the eyes; and controlling where symbols are displayed on the screenof the XR headset based on the eye-to-display relationship.
 2. Themethod of claim 1, wherein the step of determining includes determiningthe pose based on a tracking reference array attached to the XR headsetand viewable by sensors of a navigation system.
 3. The method of claim1, wherein the step of controlling includes adjusting an image displayedon the see-through screen of the XR headset based on the calibratedeye-to-display relationship.
 4. The method of claim 3, furthercomprising: obtaining a display-to-eye distortion transform relatingoptical distortion of real-world images passing through the see-throughscreen to where user eyes are posed relative to the see-through screen;and further controlling where symbols are displayed on the see-throughscreen based on the eye-to-display relationship and the display-to-eyedistortion transform.
 5. The method of claim 1, wherein determining apose of the user eyes includes determining a pose of pupils of the eyes.6. The method of claim 1, wherein the step of receiving a reflectioninclude receiving the reflection from a planar mirror.
 7. The method ofclaim 1, wherein determining a pose includes determining the pose basedon the shape of the XR headset.
 8. The method of claim 1, wherein thestep of determining a pose includes determining how far away the user isfrom the reflective surface and how far the user eyes are from thestereo cameras.
 9. The method of claim 1, wherein the step ofcontrolling includes controlling where the symbols are overlaid ontracked real-world objects.
 10. The method of claim 1, wherein: the XRheadset includes a tracking reference array viewable by sensors of anavigation system, and an image projector that projects images to bereflected by the see-through screen toward the user eyes; the step ofcontrolling includes projecting the symbols on the see-through screen tobe reflected toward the user eyes.
 11. The method of claim 1, whereinthe see-through screen is a semi-transparent screen that acts to combinereal world image with the symbols.
 12. A method of computer assistednavigation during surgery comprising: providing an extended-reality (XR)headset having stereo cameras, an image projector and a see-throughscreen for reflecting images created by the image projector for viewingby a user wearing the XR headset and for transmitting real world imagesto the user; receiving, from a reflective surface, a reflection of theXR headset by the stereo cameras of the XR headset worn by the user;determining a pose of the user eyes relative to the XR headset based onthe received reflection; calibrating an eye-to-display relationshipbased on the determined pose of the eyes; and controlling where symbolscreated by the image projector are displayed on the screen of the XRheadset based on the eye-to-display relationship.
 13. The method ofclaim 12, wherein the step of determining includes determining the posebased on a tracking reference array attached to the XR headset andviewable by sensors of a navigation system.
 14. The method of claim 12,wherein the step of controlling includes adjusting an image projectedonto the see-through screen of the XR headset based on the calibratedeye-to-display relationship.
 15. The method of claim 14, furthercomprising: obtaining a display-to-eye distortion transform relatingoptical distortion of real-world images passing through the see-throughscreen to where user eyes are posed relative to the see-through screen;and further controlling where symbols are projected onto the see-throughscreen based on the eye-to-display relationship and the display-to-eyedistortion transform.
 16. The method of claim 12, wherein determining apose of the user eyes includes determining a pose of pupils of the eyes.17. The method of claim 12, wherein the step of receiving a reflectioninclude receiving the reflection from a planar mirror.
 18. The method ofclaim 12, wherein determining a pose includes determining the pose basedon the shape of the XR headset.
 19. The method of claim 12, wherein thestep of determining a pose includes determining how far away the user isfrom the reflective surface and how far the user eyes are from thestereo cameras.
 20. The method of claim 12, wherein the step ofcontrolling includes controlling where the symbols are overlaid ontracked real-world objects.